The apparatus and methods disclosed herein are applicable, in general, to the field of material property testing, more specifically to the area of environmental conditioning of material samples or of laboratory space and instrument test zones wherein testing takes place, and most specifically, for the preferred embodiment, rapid environmental conditioning of cotton fiber, yarn, or fabric samples and the laboratories or test zones of instruments in which they are tested.
It is well known that the conditions or state of samples undergoing material property testing strongly affect test results. Rigorous and reproducible sample preparation are critical to obtaining precise and accurate test results. Major factors in sample preparation are the precision and accuracies of environmental conditions in which these steps take place. It is also well known that environmental conditions in the testing zones of materials property testing laboratories or instruments can strongly affect test results. This fact is generally important for fiber testing, and particularly critical for cotton, and other natural fibers, and for rayon, and other man-made fibers. Methods and apparatus for controlling testing zone environmental conditions are described in several U.S. patents of the first-named inventor herein and others, and in other published literature, briefly discussed below.
The prior disclosures are based in part on a recognition that it is environmental conditions within testing zones that must be accurately, precisely, cost-effectively, or optimally controlled, rather than environmental conditions in the testing laboratory. Embodiments are disclosed which enable realization of improved environmental conditions within the testing zones. Thus, Shofner U.S. Pat. No. 4,631,781, Leifeld et al U.S. Pat. No. 5,121,522, and Shofner et al U.S. Pat. No. 5,361,450, the entire disclosures of which are hereby expressly incorporated by reference, disclose improvements for the textile fiber materials processing machine step known as carding. Shofner U.S. Pat. No. 4,631,781 and Shofner et al U.S. Pat. No. 5,537,868, the entire disclosures of which are hereby expressly incorporated by reference, disclose embodiments relating to fiber testing instruments. Shofner et al U.S. Pat. No. 5,910,598, International Application No. PCT/US 95/13796 published May 17, 1996 as International Publication No. WO 96/14262, and Shofner et al U.S. Pat. No. 5,676,177, the entire disclosures of which are hereby expressly incorporated by reference, disclose improvements for textile weaving machines. Shofner et al U.S. Pat. No. 5,560,194, the entire disclosure of which is hereby expressly incorporated by reference, discloses optimal process control methods for spinning machines.
The subject invention is primarily disclosed in the context of improvements in environmental control methods and apparatus for fiber testing, which are representative of materials testing in general. Accordingly provided next is a brief background information relating to "rapid conditioning," a sample preparation step for instrument classification of cotton for HVI testing. Facilitating and improving this sample preparation step is an objective of the subject invention. Commercial embodiments of such rapid conditioning apparatus may be called "RapidCon." Another objective of the invention is to advantageously combine sample conditioning with laboratory space and instrument test zone environmental conditioning. Commercial embodiments of such multiple purpose apparatus which provides air conditioning of external laboratory space and rapid conditioning of internal test samples may be called "RapidAir."
Various United States Department of Agriculture papers describe a major improvement in fiber testing methods, known as "rapid conditioning," wherein sample condition times are reduced from 72 or 48 hours to 15 minutes or less. Examples are J. L. Knowlton and Roger K. Alldredge, "Experience with Rapid Conditioning of HVI Samples," Beltwide Cotton Conference, San Diego, Calif., January 1994; and Darryl W. Earnest, "Advancements in USDA Cotton Classing Facilities," Engineered Fiber Conference, Raleigh, N.C., May 1996.
Before this "rapid conditioning," for more than seventy-five years, certain fiber, yarn, or fabric tests have been conducted under so-called "Standard Laboratory Environment" or ASTM conditions of 65% relative humidity and 70.degree. F. (21.degree. C.) dry bulb temperature. Since what matters most, for good test results, is not conditions in the lab but conditions in the samples (and within the testing zones) at the time of testing, the various ASTM methods for fiber, yarn, or fabric samples further include the requirement that the samples to be tested be stored or "conditioned" in the standard environment for 72 hours prior to testing in the standard environment. This storage time presumably allows the samples to "reach equilibrium." It is noted that samples so conditioned are passively equilibrating, and that equilibrium usually refers to sample moisture content. Moisture content is the weight of water in the sample as a percentage of the dry weight of the sample. For cotton, equilibrium moisture content MC is about 7.3% at 65% RH, 70.degree. F. (21.degree. C.).
It should however be noted that moisture content is only one fiber, yarn, or fabric material property measurement whose equilibrium value is of interest. Others include tenacity and length (for fibers), and such material properties are much more important for selling, buying and using the fibers than is moisture content. We emphatically note that moisture content affects other fiber material properties, and is therefore an important control variable, but is not as important for marketing or utilization purposes.
Whereas equilibration times of 72 hours yield the best and most consistent test results, such periods are unacceptably long in today's intensely competitive and information-hungry marketplace. It is therefore critically important that the tests be executed accurately and precisely, that is, with minimal bias or random errors. But testing before equilibria in the tested properties are reached can disastrously (in profit/loss terms) reduce accuracy and precision. (We note that equilibrium times are different for different materials test parameters.)
Recognizing the severe conflict between promptly available results versus good (precise and accurate) results, the United States Department of Agriculture Agricultural Marketing Service, Cotton Division, began investigations in the early 1990's into actively and rapidly conditioning cotton samples. These investigations were remarkably successful and proved that well-conditioned laboratory air could be actively drawn through HVI samples (as opposed to passive or diffusional mass and heat transfer), which active conditioning or "rapid conditioning" enabled samples to reach moisture content or strength equilibrium in less than about 15 minutes. The Knowlton et al and Earnest literature references cited above provide a description. "Rapid conditioning" is now employed in most of the fourteen USDA/AMS cotton classing offices.
In our efforts to extend USDA results to small instrument classing operations having one to four HVIs (versus twenty to forty), and not having well-conditioned laboratories, we discovered that simply drawing 65%, 70.degree. F. (21.degree. C.) air through the samples for 15 minutes yielded unacceptable test results for dry and wet samples, and that unacceptably long conditioning times were required to achieve good results. We also found that sample type and size affected test results and conditioning times. Still further, we found that samples having a moisture content near 7.3% did not require much, if any, rapid conditioning. And, on a practical economic basis, we found that many small laboratories could not afford expensive laboratory or test zone environmental controls.